The usual method of construction of a metal spectacle or sunglass frame is to produce the lens retention rings, side arms and frame pieces and assemble these. Subsequently a precious metal plate layer is applied for corrosion protection.
However, because of fashion trends, coloured metal frames are sometimes required, as well as a gold or silver plating finish.
Coloured metal frames encountered on the market today have many problems associated with the coloured metal finish, and these include:
(a) poor adhesion of the plastic coat on the metal substrate, PA1 (b) thin coverage which will wear off quickly because of poor abrasion resistance, PA1 (c) inability of colour to withstand harsh solvents, and, most importantly, PA1 (d) inability to achieve a very smooth, ripple-free finish on the finished frame, and PA1 (e) absence of sufficient protection of the metal surfaces which bound the eye wire groove where the lens edge is retained, resulting in corrosion occasioned by perspiration entering the groove.
The main object of this invention is to provide improvements in the application of a colour coating which will reduce these problems in the production of coloured metal frames.